Suppliers of gas turbine systems for power generation typically contractually guarantee certain performance conditions. That is, a contract between a supplier and a customer can specify certain performance conditions for a gas turbine system or unit to be provided to the customer. Computer models can be used to determine the performance conditions when bidding for a contract. The modeling can be typically set up to represent a nominal average gas turbine system or unit, but inevitably, there may be variations in a nominal average gas turbine system or unit and the system or unit that is ultimately installed because of hardware variations and measurement uncertainties and other circumstances. Accordingly, every gas turbine system or unit may not perform according to nominal performance modeling.
Once a gas turbine system or unit is installed, the supplier can perform an integrated tuning test and can collect data on the installed gas turbine system or unit. Using this data, the supplier may attempt to determine how different the gas turbine system or unit is performing from a nominal average gas turbine system or unit. An attempt can be made to tune the installed gas turbine control system or unit such that the performance conditions stated in a contract with the customer may be met.
One conventional control methodology used by a supplier to tune an installed gas turbine system or unit is called an exhaust temperature based control. In certain control systems, a control curve can be implemented with an exhaust temperature target versus compressor pressure ratio. Based on that curve shape, the firing temperature can be determined at ambient conditions. Adjusting the curve up or down can adjust the firing temperature and the gas turbine system or unit can operate at a new ambient condition. Similarly, the supplier may change the inlet guide vane (IGV) maximum open condition to adjust the amount of airflow the gas turbine system or unit will allow. However, the conventional control methodology described above only uses a single control loop across all ambient conditions so adjusting the performance settings at one set of test conditions can automatically affect the contract conditions as well. For a specific gas turbine system or unit deviating from the nominal performance conditions, nominal control schedules may not perform in a desired way. This variation may require the schedules to be updated, so the gas turbine system or unit can perform as intended at the contract performance conditions.